Heat exchanger



IN VEN TOR. )ix/@1417 y /mrawvy H. F. ROHMANN HEAT EXCHANGER Filed Oct.28. 1948 April 7, 1953 Patented Apr. 7, 17953 HEAT EXCHANGER Henry F.Rohmann, Evansville, Ind., assignor to Servel, Inc., New York, N. Y., acorporation of Delaware Application October 28, 1948,l Serial No. 56,972

The'present invention relates to refrigeration and more particularly toa heat exchanger construction.

YThe heat exchanger of the present invention is particularly adapted foruse in the absorption liquid circuit of absorption refrigeration'systems of the type used in household refrigerators but is notnecessarily limited to such use or even to usejin an absorption typerefriger- -ation system.

The object of Vthe present invention is to provide a heat exchanger ofimproved construction which adapts it for economical manufacture. Theimprovement resides in forming a heat exchanger by merely telescopingthe ends of intermediate tubes between the ends of concentric tubes andwelding the joints therebetween. While the parts may be welded in anysuitable manner, the invention also includes a method of fabrication bywhich the parts are welded into an integral structure by a singlebrazing operation.

The above objects will become more apparent from the followingdescription and drawing in which like 'reference characters denote likeparts throughout the several views. It is to be understood, however,that the drawing is for the purpose of illustration only and not adenition of the limits of the invention, reference being had for thispurpose to the appended claim. In the drawing:

Fig. 1 is a diagrammatical view of an absorption refrigeration systemincorporating the heat exchanger of the present invention; Fig. 2 is alongitudinal sectional view of the ends of the heat exchanger showingintermediate tubes telescoped between the ends of inner and outerconcentric tubes and'welded together to seal the joints therebetween;and

Fig. 3 is a transverse sectional view taken on line 3"-3 of Fig. '2 andshowing the inner and outer chambers of the heat exchanger. Y

In the drawing, the heat exchanger of the present invention is shownembodied in an absorption refrigeration Vapparatus of a uniform pressuretype utilizing a refrigerant, an absorbent and an auxiliary pressureequalizing gas. Apparatus ofV this type` is well known and comprises agenerator 5, a condenser t, an evaporator 1, a gas heat exchanger 8,absorber 9 yand liquid heat exchanger Ill. The generator '5 has a iluell and 'aKA shell I2 surrounding the flue to providea chamber I3therebetween. The generator 51s heated by a gas burner I4 which projectsa naine into thel'ue II and refrigerant is expelled from absorptionsolution in the 1 Claim. (Cl. 257-246) chamber I3 by heat transmittedthrough the wall of the ue. Refrigerant vapor flows from the generator 5through a conduit I5 connecting the upper end of chamber I3 to the upperend of the condenser 6. The condenser 6 is in the form of a pipe coilhaving a plurality of loops with spaced ns I6 thereon and the condenseris cooled by air flowing between the ns I6 and over the pipe coil.Refrigerant vapor is condensed in the condenser 6 and flows-from thebottom of the condenser to the top of the evaporator 'i through aconduit I1. The evaporator is illustrated in the form of a verticallyarranged pipe coil and the refrigerant flows from the top to the bottomby gravity.

Absorption liquid from which refrigerant has been expelled flows bygravity from the bottom of the chamber I3 of the generator 5 to the topof the absorber 9 in a path of ow comprising a conduit I8, outer passageof the liquid heat exchanger I0 and conduit I9. The absorber alsocomprises a vertically arranged pipe coil having iins 20 and theabsorption liquid weak in refrigerant ows by gravity through theabsorber and into an absorber pot 2l connected to its lower end. Theabsorption liquid absorbs vrefrigerant vapor as it ows through theabsorber 9, as later explained in detail, and the absorber is cooled byair llowing between the iins 20 and over the pipe coil. .Absorptionliquid strong in refrigerant flows from the absorber pot 2| to thegenerator 5 in a lpath of flow comprising a conduit 22,.inner passage oithe heat exchanger I0, coil 23 surrounding the lower end of thegenerator ue II and vapor lift tube 24 connected to the chamber I3 ofthe generator 5 adjacent its top. Thus, relatively cool absorptionliquid owing from the absorber pet 2| is heated by the relatively hotabsorption solution flowing from the generator 5 in the heat exchangerI0 and solution in the coil 23 is heated by the flue II to expelrefrigerant vapor therefrom and lift the solution to a higher level asit is delivered to thegenerator 5 to cause it to flow by gravity throughthe absorption liquid circuit.

The liquid refrigerant evaporates in the evaporator 'l and diffuses intoa gas such as hydrogen at partial pressure to produce a refrigeratingeffect in the insulated refrigerator cabinet 25. Thepressure equalizinggas is introduced into the bottom of the evaporator from the outerpassage 26 of the gas heat exchanger 8. The mixture of refrigerant vaporand pressure equalizing gas flows from the top of the evaporator 5andthen downwardly through the in- 3 ner passage 21 of the gas heatexchanger int-o the absorber pot 2|. The mixture of refrigerant vaporand pressure equalizing gas then ows upwardly from the absorber pot 2|through the absorber 9 in a direction countercurrent to the iiow ofabsorption solution. Due to the affinity of the refrigerant andabsorbent the refrigerant vapor is absorbed into the absorption solutionand the pressure equalizing gas flows from the top of the absorber intothe outer passage 23 of the gas heat exchanger 8 to complete its cycleof operation. A pressure vessel 28 is also provided in the gas circuitwhich is connected between the outlet from the condenser and the innerpassage 2 of the gas heat exchanger 8v for regulating the pressure inthe system in ac cordance with changes in operating conditions as wellunderstood in the art.

In accordance with the present invention, the liquid heat exchanger lcomprises an inner tube 30 and an outer tube 3| with the ends 32 and 33of conduit 22 and coil 23, respectively, telescoped therebetween as mostclearly shown in Fig. 2. Preferably, the inner tube 30 is slightlylonger than the outer tube 3| and the ends 32 and 33, constitutingintermediate tubes, extend into the outer tube 3| for a short distance.Thus, the inner tube 30, outer tube 3| and intermediate tubes 32 and 33'overlap each other at each end of the heat exchanger i9 and theintermediate tubes have substantially the same inside and outsidediameters as the outside and inside diameters of the inner and outertub-es, respectively, so as to provide a close t between the parts.Suitable inlet and outlet ports 34 and 35 are provided at opposite endsof the outer tube 3| for receiving the ends of conduits I8 and I9,respectively.

In its broadest aspect the invention comprises joining the ends of theinner tube 30, outer tube 3| and intermediate tubes 32 and 33 in anysuitable manner, such as welding, brazing or soldering, to connect theparts into an integral structure and seal the joints therebetween.Preferably, however, the tubes of iron or steel are all joined by asingle brazing operation. For this purpose the parts are rst assembledby telescoping the intermediate tube 32, either -as an integral part ofconduit 22 or as a nipple to be later connected to the conduit, betweenthe inner and outer tubes 30 and 3| at one end and telescoping theintermediate tube 33, either as an integral or separate part of coil 23,between the inner and outer tubes at the opposite end. A eutectic ironphosphide brazing material as described in the co-pending applicationfor United States Letters Patent of Robert S. Taylor et al., Serial No.660,126, filed April 5, 1946, now Patent No. 2,487,001, is then appliedto each joint. The brazing material may be applied as a paste ofpowdered alloy mixed with a binder or as briquettes of compactedpowdered alloy or as a solid metal. The assembly is then heated to themelting temperature of the brazing material which flows by capillaryaction fbetween the parts to completely seal the joints J as illustratedin Fig. 2. Joints J of iron phosphide alloy have been found to be asstrong as the iron and steel tubes which they bond but the alloy isquite brittle and is apt to cra-ck if deformed as by bending. The heatexchanger construction of the present invention, however, reinforces thejoints J so that any bending which might tend to crack the bondingmaterial will occur at a place remote from the joints.

The heat exchanger I0 may be fabricated as a su-bassembly or may befabricated with other elements such as the generator 5 and absorber 9 ina larger sub-assembly or the entire unit may be fabricated by a singlebrazing operation. Thus, the heat exchanger I0 has a novel structurewhich facilitates assembly of the parts and the novel construction isparticularly adapted for fabrication by a single brazing operation as itprovides a resulting structure which reinforces the brazed joints J.

In operation the inner tube 30 and intermediate tubes 32 and 33,constituting the ends of conduit 22 and coil 23, respectively, providethe path of flow for absorption solution strong in refrigerant flowingfrom the absorber 9 toward the generator 5 and the annular chamber 36between the inner land outer tubes 30 and 3|, together with the conduitsI8 and I9, provide the path of flow for absorption solution weak inrefrigerant owing from the generator toward the absorber.

While a single form of the invention is herein illustrated and describedit will be understood that modications may be made in the constructionand arrangement of parts without departing from the spirit or scope ofthe invention. For example, the term tube as used in the specication andclaim is intended to include oval or flattened tubes as well ascylindrical tubes. Therefore, without limitation in this respect, theinvention is defined by the following claim.

I claim:

A heat exchanger connected between elements in a refrigeration systemcomprising an inner section of ordinary tubing, an outer section ofordinary tubing, and intermediate sections of ordinary tubing telescopedbetween and extending from the inner and outer tubing sections atopposite ends thereof, the inner and outer peripheries of saidintermediate tubing sections having a close t with the inner and outertubing sections to provide capillary spaces therebetween. a eutecticiron-phosphorus alloy in said capillary spaces to seal the joints, inletand outlet ports adjacent the opposite ends of the outer tubing section,the interior of the inner tubing section providing one path of flow andthe annular chamber between the inner and outer sections providing asecond path of flow in heat exchange with the first path of flow, andthe intermediate tubing sections forming extensions of the path of ilowthrough the inner tubing section and adapted to be connected to otherelements of the refrigeration system.

'HENRY F. Roi-MANN.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 235,834 White Dec. 2l, 1880318,971 Evans June 2, 1885 519,193 Muller Y May 1, 1894 1,016,582Schneider Feb. 6, 1912 1,024,436 Cartault Apr. 23, 1912 1,197,858 RedmonSept. 12, 1916 1,809,075 Scovel, Jr. June 9, 1931 2,152,812 Money Apr.4, 1939 2,487,001 Taylor et al. Nov. l, 1949 2,503,595 Preston Apr. 11,1950

